1. Field of the Invention
This invention relates to fittings and in particular to an axial swage fitting for pipes and tubes.
2. Description of Related Art
Fittings of various types are commonly used to couple tubes and pipes for a variety of applications. For example, in the aerospace industry, swage fittings are used to couple hydraulic lines, fuel lines, and the like, which convey fluids in aircraft and other vehicles. The coupling generally involves the deformation of a portion of the tube or pipe and the deformation of the fitting in response to the application of a swaging force to the fitting. The swage methodology is described in numerous patents, for example, U.S. Pat. No. 3,675,949 and U.S. Pat. No. 3,893,718.
Various fittings have been developed which use the above referenced methodology to connect tubes. For example, U.S. Pat. No. 4,482,174 discloses an apparatus having a sleeve and a locking slidable over at least the first end of the sleeve, which has a reverse taper configuration. In another example, U.S. Pat. No. 5,110,163 discloses a fitting, which generally includes a sleeve having a tapered outer surface, and a swaging ring, which may be urged over the tapered surface to secure pipes together. In yet another example, U.S. Pat. No. 5,452,921 discloses a fitting, which includes a sleeve having a tapered outer surface, and a swaging ring, having a matching tapered surface. During swaging, the swaging ring is moved axially over the sleeve, such that the tapered surfaces interact to apply a radial force on the sleeve inwardly into the pipe to make a swaged connection.
Although, swage fittings are well known in the industry, swaging techniques are not widely used on pipes and tubes with large diameters, in high pressure applications. One reason for this is that, existing swaged fitting designs generally lack the requisite pipe retention capability, necessary for large bore, high pressure applications. Moreover, since most swaged fittings are not designed for large bore pipes, the swaging force necessary to deform the sleeve and pipe during swaging, is usually beyond the capability of existing swaging tools. The high strength and force requirements of such applications, tend to drive the relative size of the fitting, the swaging time, and the costs associated with manufacture, to prohibitive levels.
Another reason that the use of swaged fittings has generally gone unexplored for use with large diameter bore pipes, in high pressure applications, is that alternative, conventional, non-swaging means already exist for these applications. Generally, large bore pipes and tubes, used in high pressure applications, may be coupled together using welds, flange and bolt connections, and threaded engagements. Although, these types of connections are commonplace, they are generally plagued with a variety of drawbacks, which make them high cost, high risk, and/or time consuming alternatives to the present invention. For example, welded pipe joints usually require additional pre- and post-weld preparation events that are usually expensive and time consuming, such as pipe end preparation, post weld, grinding, non destructive inspection and hydro-testing. Welds in pipes have also been known to fail at weak spots in heat affected areas adjacent to the welds. Moreover, welding in the vicinity of potentially flammable fluids such as fuel and oil which may be used in the pipes or tubes, is inherently risky. Flanged and bolted connecting systems require that the pipe ends be flared prior to use which may be inconvenient, expensive, and time consuming. To create the joint, the flanges are bolted together with a gasket in between to provide a seal. In many instances vibrations or other general usage may loosen bolts and cause leaks. Moreover, gaskets are prone to failure after time or are easily damaged, which may further result in leaks. Threaded systems, require pipe ends to be threaded, which can be time consuming and ineffective. Generally, an abundance of access space is necessary for using wrenches and the like to couple the threaded pipes. Typically, a sealant is used on the threads to fill gaps and prevent leaking. However, after a period of time, the sealant can deteriorate, which leads to leaking.
For the above reasons, what is needed is an axially swaged fitting that provides an improved coupling and sealing capability between pipes and tubes, especially large bore pipes and tubes for use in high pressure applications.
The present invention provides a fitting for joining pipes, tubes, or conduits (hereinafter collectively xe2x80x9cpipesxe2x80x9d). Preferably, the fitting improves couplings of a large bore pipe, generally of 2 inches and larger in diameter. The improved coupling capability is a result of an enhanced tensile strength capacity in the fitting that keeps forces, which may result from high burst pressures and the like, from pulling a pipe axially away from the fitting The fitting includes a substantially cylindrical sleeve, which has an inner surface defining a bore, configured to slidably receive the pipe at an open end. The inner surface of the sleeve includes protrusions, which grip the outer surface of the pipe upon swaging. The outer surface of the sleeve includes multiple stepped lands of ascending height relative to the open end. The fitting further includes a substantially cylindrical swaging ring. An inner surface of the swaging ring includes multiple contact surfaces of descending height configured to engage the multiple ascending steps on the sleeve with an interference fit. Axial motion of the swaging ring causes the swaging ring to slide over the sleeve and apply a radial swaging force directly to the multiple stepped sleeve. The swaging force makes the ring overcome the interference and inwardly push the multiple ascending steps of the sleeve, which swages the sleeve to the pipe. Advantageously, the multiple ascending steps of the sleeve are positioned relative to the descending steps of the ring, such that only one stepped portion at a time is swaged.
One embodiment of the present invention is a fitting for joining pipes by swaging. The fitting includes a sleeve which defines a bore, which is sized to receive a pipe. The sleeve has an inner surface and an outer surface. The outer surface includes a first stepped portion, which has a first dimension, and a second stepped portion, which has a second dimension. The fitting also includes a ring, which has an inner surface configured to engage the first and second stepped portions. While engaging the first stepped portion the ring alters the first dimension and, while engaging the second stepped portion, alters the second dimension which causes the sleeve to be swaged to the pipe.
In another embodiment of the present invention is a fitting for attachment to a pipe by swaging. The fitting includes a sleeve and a ring. The sleeve defines a bore configured to receive a pipe and has an outer surface, with a first stepped portion and a second stepped portion. The ring has an inner surface including a first contact portion configured to deform the first stepped portion, and a second contact portion configured to deform the second stepped portion in response to an axial movement of the ring.
In yet another embodiment of the invention, a method for joining pipes by swaging includes deforming a first stepped portion of a sleeve with a radial swaging force provided by a swaging ring; and thereafter deforming a second stepped, portion of the sleeve with the radial swaging force provided by the swaging ring.
The present invention provides many advantages over other swaging techniques. Since the multiple ascending steps of the sleeve may be swaged one step at a time, the swage force required to create a seal may be minimized. The fitting couples pipes in a safer more reliable, and easier to use, manner than do most current pipe coupling methods and devices. Advantageously, the fitting may be locked into position to ensure that the fitting stays in position while experiencing vibrations or other adverse environmental effects. Moreover, the fitting provides a hermetical seal that can be made relatively quickly and cost effectively for the rated pressure of the pipe being joined. The seal also provides substantial torque resistance.
These and other features and advantages of the present invention will be more readily apparent from the detailed description of the preferred embodiments set forth below taken in conjunction with the accompanying drawings.